1. Field of the Invention
The present invention generally relates to power tools, and, more specifically, to a grinder attachments for existing precision grinding machines.
2. Description of the Prior Art
Grinding machines may be classified as cylindrical, internal, centerless, surface and special grinders, based on the general character of the work. Each of these classes may be further subdivided according to special characteristics either of work or machine. For example, surface grinding machines may include a horizontal spindle or a vertical spindle and may vary from small tool-room machines, using 7 by 1/2 in. wheels, to massive face grinding machines using 48 and even 60 in. diameter chucks.
The work is supported on tables, equipped with either hand or power feed. The spindles are driven either directly from the motor or through belt drives.
Face grinders are a form of surface grinder in which the work travels past the side of a wheel, carried on a horizontal spindle mounted at right angles to the line of travel of the work The wheel grinds the vertical surface of the work at right angles to the surface of the table. The table is traversed hydraulically, and the wheel is driven by silent chain or V belt. Work can be held by bolting to the table or to angle plates or by magnetic chucks. These machines are used for surface grinding and for the grinding of machine knives, shear blades, etc. Tables range from 22 to 27 in. wide and from 60 to 168 in. long.
Grinding tolerances have decreased with improvements in grinding machines, grinding wheels and gauging devices. On cylindrical grinding machines, for example, tolerances in diameter of .+-.0.00001 in. are possible when an automatic sizing device similar to a Nortonizer (Norton Co.) is used, if the machine and temperature conditions approach ideal. In out-of-roundness and taper, tolerances as small as 0.00005 in. are practical. Readily held tolerances, however, range from around .+-.0.0001 in. to 0.0005 in., with the surface finish as fine as 4 to 5 micro inches rms. While other operations, such as honing and lapping, may be used to refine the grinding of cylindrical surfaces and produce exceedingly smooth and highly accurate surfaces, it is sometimes desired to provide grinding with relative tight tolerances. While such tolerances may readily be achieved with a high quality fixed grinder, such as an Okamoto grinder, loss of precision may easily result when attachments are connected to the grinder for converting the speed of rotation of the grinder spindle from the nominal to a different rotational speed. In some cases, because of the nature of the grinding operation, a higher rotational speed of the abrasive grinding element is required. While an attachment has been known for connection to an existing fixed grinding machine for converting the rotational speed of the grinder, typically enhancing or increasing the operating speed of the abrasive element the known grinder attachment, sold by Speedline Industries, Inc., of Clinton Township, Mo., has not been useful for precision grinding operations. The known grinder attachment was made of cast aluminum, and deformed under stress. Also, the means for securing the attachment to the fixed grinder has not prevented the attachment from moving relative to the fixed grinder housing or head. Because of both of these reasons, the abrasive grinding element mounted on the attachment has been subjected to excessive vibrations, movements and deflections relative to the fixed grinder head. These movements do not permit precision grinding at high tolerances.